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Alexandre Tchernev
On the grades of order ideals
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Published: |
April 12, 2005
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Keywords: |
Order ideals, syzygies, syzygy theorem |
Subject: |
13D02, 13D22 |
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Abstract
Let R be a commutative Noetherian local ring, let M be
a finitely generated R-module of finite projective
dimension, and let u∈ M be a minimal generator of M.
We investigate in a characteristic free setting the
grade of the order ideal OM(u)={f(u) | f∈HomR(M,R)}.
The main result is that when M is a k-th syzygy module and
pdR M≦ 1 then gradeR OM(u)≧ k; in particular if
M is an ideal of projective dimension at most 1 then
every minimal generator of M is a regular element of R.
As an application we show that the
minimal generators of M are regular elements of R
also in the case when M is a Gorenstein ideal of grade 3,
in the case when M is a three generated ideal,
and in the case
when M is an almost complete intersection ideal
of grade 3 and R is Cohen-Macaulay.
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Author information
Department of Mathematics, University at Albany, SUNY, Albany, NY 12222
tchernev@math.albany.edu
http://math.albany.edu:8000/~tchernev/
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